Another classic textbook of protozoology. Although a little bit
outdated, it contains many useful information and numerous pictures
and figures. I found the 'Ecology of Protozoa' chapter particularly interesting.
Many references.

16) A Field Guide to Bacteria, Betsey Dexter Dyer, Cornell University Press, 2003

A fascinating book describing free-living species of bacteria.

17) Exploring with the microscope. A book of discovery and learning., Werner Nachtigall,
Sterling Publishing Co., Inc., New York, 1996

Amazing book on microscopy and photomicrography of various subjects.
Includes very extensive introduction to microscopy and covers many advanced topics.
Includes keys for identification of aquatic microorganisms. Illustrated with
hundreds of beautiful photographs.